Shining light into the Higgs portal with $$\gamma \gamma $$ colliders

Abstract

AbstractHigh-energy $$\gamma \gamma $$ γ γ colliders constitute a potential running mode of future lepton colliders such as the ILC and CLIC. We study the sensitivity of a high-energy $$\gamma \gamma $$ γ γ collider to the Higgs portal scenario to a hidden sector above the invisible Higgs decay threshold. We show that such $$\gamma \gamma $$ γ γ collisions could allow to probe the existence of dark sectors through the Higgs portal with precision competitive with other planned collider facilities, profiting from the unique combination of sizable cross-section with clean final state and collider environment. In addition, this search could cover the singlet Higgs portal parameter space yielding a first-order electroweak phase transition in the early Universe.